Hi Ed, I do want to add a function called "Tapered extrude" which I think is what you are talking about. Originally I had hoped to include this for v2 but it does not look like that will happen currently, so probably in v3.

You can actually get the same result though currently by using Offset on the curve, then moving the offset in the Z direction and doing a Loft. Check out this previous post for an example:
http://moi3d.com/forum/index.php?webtag=MOI&msg=941.5

- Michael